Scientists discover exact receptor for DEET that repels mosquitoes

DEET has been the gold standard of insect repellents for more than six decades, and now researchers led by a University of California, Davis, scientist have discovered the exact odorant receptor that repels them.

fig. Biochemist Walter Leal has discovered which receptor on mosquito antennae detects DEET, making it an effective repellant.

They also have identified a plant defensive compound that might mimic DEET, a discovery that could pave the way for better and more affordable insect repellents. Findings from the study appear in the journal Proceedings of the National Academy of Sciences.

More than 200 million people worldwide use DEET, developed by scientists at the U.S. Department of Agriculture and patented by the U.S. Army in 1946.

A gut bacterium that attacks dengue and malaria pathogens and their mosquito vectors

Just like those of humans, insect guts are full of microbes, and the microbiota can influence the insect's ability to transmit diseases. A study published on October 23rd in PLOS Pathogens reports that a bacterium isolated from the gut of an Aedes mosquito can reduce infection of mosquitoes by malaria parasites and dengue virus. The bacterium can also directly inhibit these pathogens in the test tube, and shorten the life span of the mosquitoes that transmit both diseases.

George Dimopoulos and colleagues from Johns Hopkins University, USA, had previously isolated Csp_P, a member of the family of chromobacteria, from the gut of Aedes aegypti mosquitoes (which transmit dengue fever) in Panama. In the present study, they examined its actions on both mosquitoes and pathogens, and the results suggest that Csp_P might help to fight malaria and dengue fever at different levels.

Genetic tweak gave yellow fever mosquitoes a nose for human odor

One of the world's deadliest mosquitoes sustains its taste for human blood thanks in part to a genetic tweak that makes it more sensitive to human odor, according to new research.

 

 image : Researchers report that the yellow fever mosquito sustains its taste for human blood thanks in part to a genetic tweak that makes it more sensitive to human odor. The human-preferring 'domestic' form of the mosquito (right) contains a version of the odor-detecting gene AaegOr4 in its antennae that is highly attuned to sulcatone, a compound prevalent in human odor. The researchers found that this gene is more abundant and more sensitive in the domestic form than in its ancestral 'forest' form (left), which prefers the blood of non-human animals. Credit: Carolyn McBride, Department of Ecology and Evolutionary Biology and the Princeton Neuroscience Institute

Researchers report in the journal Nature that the yellow fever mosquito contains a version of an odor-detecting gene in its antennae that is highly attuned to sulcatone, a compound prevalent in human odor. The researchers found that the gene, AaegOr4, is more abundant and more sensitive in the human-preferring "domestic" form of the yellow fever mosquito than in its ancestral "forest" form that prefers the blood of non-human animals.

The research provides a rare glimpse at the genetic changes that cause behaviors to evolve, explained first author Carolyn "Lindy" McBride, an assistant professor in Princeton University's Department of Ecology and Evolutionary Biology and the Princeton Neuroscience Institute who conducted the work as a postdoctoral researcher at the Rockefeller University. Uncovering the genetic basis of changes in behavior can help us understand the neural pathways that carry out that behavior, McBride said.

Number of people susceptible to painful mosquito-borne virus increasing, says leading researcher

In just two weeks, the number of Americans infected with the mosquito-borne virus chikungunya has almost doubled and the virus has now been found in mosquitoes in the United States, something that is very concerning to a Kansas State University professor who is a leading researcher of the virus.

At least 243 travel-related cases of chikungunya have been reported to the Centers for Disease Control and Prevention in 31 states, with the number expected to grow. The first case acquired in the United States was reported in Florida, seven months after the mosquito-borne virus was recognized in the Western Hemisphere.
Stephen Higgs, one of the world's leading researchers of the virus and director of Kansas State University's Biosecurity Research Institute, says many more people are now at risk of becoming infected.

Zika virus: New threat from tiger mosquito

In the group of viruses that includes dengue and chikungunya, a newcomer now has people talking about it. Also originating in Africa, zika was isolated in humans in the 1970s. Several years earlier, only a few human cases had been reported. It took until 2007 for the virus to show its epidemic capacity, with 5,000 cases in Micronesia in the Pacific, and then especially, at the end of 2013 in Polynesia, where 55,000 people were affected. In light of these recent events, researchers from IRD and the CIRMF in Gabon restarted work on the concomitant dengue and chikungunya epidemic that occurred in 2007 in the capital, Libreville, and which affected 20,000 people. Showing almost the same symptoms as its two dreaded cousins, did zika pass unnoticed by the researchers?

Climate, genetics can affect how long virus-carrying mosquitoes live

It's just math: The longer a mosquito lives, the better its odds of transmitting disease to humans or animals.

But as it turns out, factors such as the mosquito's own genetics and the climate it lives in have a big -- albeit complicated and not wholly understood -- role to play in its lifespan.
University of Florida researchers, hoping to better understand how West Nile virus affects mosquitoes, set up an experiment they outline in the Journal of Vector Ecology's current issue.
Mosquitoes can transmit any number of pathogens to humans, including protozoan malaria, West Nile, dengue and chikungunya viruses. Malaria cases range between 350 million and 500 million each year, with 1 million to 3 million deaths every year.
In the experiment, UF researchers examined survival rates for mosquitoes from two laboratory-reared colonies, one from Gainesville and one from Vero Beach.
Half of each of the mosquito colonies was fed West Nile virus-infected blood, the other half kept as a control population, and fed blood without the virus.
They divided the groups once more, this time keeping the mosquitoes at two temperatures, one group at 80.6 degrees, the other at 87.8 degrees Fahrenheit -- a rather large difference in temperature for cold-blooded insects.
Their findings were both unexpected and illuminating, said Barry Alto, a UF assistant professor of arbovirology based at the Florida Medical Entomology Laboratory in Vero Beach.

Gene differences in yellow fever, malaria mosquitoes mapped

Virginia Tech entomologists have developed a chromosome map for about half of the genome of the mosquito Aedes agypti, the major carrier of dengue fever and yellow fever.

With the map, researchers can compare the chromosome organization and evolution between this mosquito and the major carrier of malaria, the Anopheles gambiae mosquito, to find ways to prevent diseases.
"Despite looking somewhat similar, these mosquitoes diverged from each other about 150 million years ago. So, they are genetically further apart than humans and elephants," said Maria Sharakhova, a research scientist in the College of Agriculture and Life Sciences, a Fralin Life Science Institute affiliate, and the principal investigator of the study published in BMC Biologyand highlighted on Biome.